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Miniaturized broadband spectrometer based on a three-segment diffraction grating for spectral tissue sensing

Gebirie Yizengaw Belay, Willem Hoving, Arthur van der Put, Michael Vervaeke, Jürgen Van Erps, Hugo Thienpont, Heidi Ottevaere

Optics and Lasers in Engineering, 2020

26 citations

Abstract

Compact and broadband spectrometers are very useful in various application domains such as agriculture, food, health and security. In minimally-invasive image-guided procedures spectral tissue sensing helps for screening and diagnostic purposes aiming at discriminating between healthy and tumorous tissue at point-of-care locations and outpatient centers. We designed a compact spectrometer based on a three-segment diffraction grating which operates from 300 nm to 1700 nm. The first two segments of the grating cover spectral ranges from ultraviolet to visible and near infrared (UV, VIS/NIR), whereas the third segment covers the short-wave infrared (SWIR) region from 830 nm to 1700 nm. The spectrometer has a resolution of 6 nm in the UV-VIS/NIR ranges and 10 nm in the SWIR range. The smallest signal-to-noise ratio (SNR) of the spectrometer achieved in the VIS range is 650 and in the SWIR range 9300. Afterwards, the designed three-segment grating was fabricated in-house with ultra-precision diamond tooling followed by hot embossing and quantitatively characterized. The experimental results show that the three-segment grating improves the diffraction efficiency in the NIR-SWIR wavelength range by at least a factor of 2 compared to a Richardson grating which only operates from 300 nm to 1100 nm. This result paves the way towards a new approach for making compact and low-cost spectrometers which could be integrated with hand held devices such as tablets and smartphones.

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